The present invention relates to an optical pickup device for recording or reproducing data on/from optical disks.
In recent years, optical disks capable of storing enormous amounts of data at high density have been used in various fields. Optical disks are optical data storage mediums characterized by the capabilities of non-contact data recording or reproduction, and medium interchange. Especially, optimal disks have received attention as external storage mediums for optical disk files or computers.
On optical disks, data are recorded or reproduced by an optical pickup using a semiconductor laser or the like, and the recorded data can be erased and rewritten on some optical disks.
FIG. 21 is a schematic diagram illustrating the structure of a conventional optical pickup device 500. The optical pickup device 500 is provided with a data recording/reproduction means 502, and a driving means 512 for driving the data recording/reproduction means 502. The data recording/reproduction means 502 is provided with a light source holder for recording or reproducing data on/from a disk type recording medium 511 that rotates about an axis 510, and a fine-adjustment means 504 for finely adjusting the position of the light source holder 503. The light source holder 503 is provided with a laser beam emission/reception means 515, a reflection mirror 505, an object lens 506, an object lens holder 507, and an object lens position adjustment means 508.
The data recording/reproduction means 502 is driven, by the driving means 512, in the direction of the radius of the recording medium 511, and records or reproduces data on/from an arbitrary area of the recording medium 511. The laser beam emission/reception means 515 emits a laser beam 519, and receives the laser beam 519 reflected at the recording medium 511. The reflection mirror 505 is a plane mirror that reflects the laser beam 519. The object lens 506 converges the laser beam 519 reflected by the reflection mirror 505, onto the signal recording surface of the recording medium 511. The object lens holder 507 holds the object lens 506. The object lens position adjustment means 509 drives the object lens holder 507 in the direction perpendicular to the data recording surface of the recording medium 511 so as to bring the laser beam 519 into a focus on the signal recording layer of the recording medium 511.
In the optical pickup device 500 so constructed, except for an auxiliary laser beam for track servo, a single laser beam 519 is focused on a single recording track on the recording medium 511, and reading/writing of data from/into the signal recording track is carried out at one time. In this case, since the recording rate or reproduction rate of the optical pickup device 500 to the recording medium 511 depends on the rotation speed of the optical disk, the recording medium 511 must be rotated at a high speed to increase the recording rate or reproduction rate. Therefore, prevention of vibrations caused by that the recording medium 511 is out of balance, and speedup in signal processing are desired.
FIG. 22 is a schematic diagram illustrating a conventional optical pickup device 501 that can perform reading or writing of data from/into plural recording tracks at the same time. In FIG. 22, the same reference numerals as those shown in FIG. 21 denote the same or corresponding parts. The light source holder 503 further includes a diffraction grating 509 and a diffraction grating adjustment means 515. The diffraction grating 509 splits the laser beam 519 into plural laser beams 514 that are nearly parallel to each other. The diffraction grating adjustment means 515 finely adjusts the diffraction grating 509 so that splitting of the laser beam 519 is appropriately carried out.
As described above, in the optical pickup device 501 shown in FIG. 22, the diffraction grating 509 splits the laser beam 519 into the nearly-parallel laser beams 514, and data are read or written from/into plural recording tracks at the same time using the laser beams 514, whereby high-speed reading/writing is achieved without increasing the rotation speed of the recording medium 511. A birefringence material may be used instead of the diffraction grating 509.
In the conventional optical pickup device 500 or 501, the focal length in the focusing direction and the focal direction in the tracking direction must be controlled by the object lens adjustment means 508 and the fine-adjustment means 504, respectively, to bring the laser beam 519 into a focus on the data recording layer of the optical disk 511. Especially in an optical disk recording apparatus or an optical disk reproduction apparatus that is applicable to both a DVD (Digital Versatile Disk) and a CD (Compact Disk), since the position of a data a recording layer in a recording medium in the vertical direction of the medium (hereinafter referred to as xe2x80x9cdepth positionxe2x80x9d) differs between the DVD and the CD due to the difference in their standards, the object lens adjustment means 508 is necessary to bring a laser beam into focuses on the respective data recording layers of the DVD and the CD. Therefore, mechanical driving by the object lens adjustment means 508 and the fine-adjustment means 504 is necessary to control the position of the focus of the laser beam, and excess time and energy for the mechanical driving are required.
Further, in order to bring a laser beam into focuses on the data recording layers of the DVD and the CD, a double-focus lens that can bring a laser beam into the respective focuses may be employed as an object lens, instead of the object lens adjustment means 508. In this case, however, a signal from one focus is inputted as noise to a signal from the other focus, resulting in degraded signal quality.
Further, in order to record or reproduce data on/from an arbitrary area of the data recording medium 511, the data recording/reproduction means having a weight including the weights of the object lens adjustment means 508 and the fine-adjustment means 504 must be driven by the driving means 512. Therefore, excess time and energy are required for driving the data recording/reproduction means 502.
Furthermore, in the conventional optical pickup device 501, when plural laser beams are emitted, the intervals of focuses of the respective laser beams are fixed by the physical arrangement of the respective constituents, or it is only possible to change the intervals of focuses of all laser beams 514 at the same time by the diffraction grating 509. Accordingly, for example, in a three-beam system optical pickup device, although two beams can be brought into focuses on recording tracks, the focus position of the third beam alone cannot be controlled independently. In some cases, reading of data by the third beam cannot be carried out unless using a technique that can read data even when the focus of the beam is not positioned on the recording track, such as an image sensor or the like.
The present invention is made to solve the above-mentioned problems and has for its object to provide an optical pickup device that realizes speedup and energy saving in driving the data recording/reproduction means with the driving means by reducing the weight of the data recording/reproduction means, that realizes speedup and energy saving in controlling the position of focus of a laser beam by performing the control without using mechanical driver, and that is able to adjust the positions of focuses of plural laser beams independently.
Other objects and advantages of the invention will become apparent from the detailed description that follows. The detailed description and specific embodiments described are provided only for illustration since various additions and modifications within the scope of the invention will be apparent to those of skill in the art from the detailed description.
According to a first aspect of the present invention, there is provided an optical pickup device for irradiating a data recording layer of a disk type data recording medium with a laser beam emitted from a light source, comprising: an object lens comprising a transparent piezoelectric element that deforms when a voltage is applied, and condensing the laser beam emitted from the light source to apply it onto the data recording layer; and control means for controlling the position of focus of the laser beam by applying a voltage to the object lens to deform the object lens. In the optical pickup device so constructed, focusing of the laser beam and tracking can be electrically carried out, and a mechanism for driving the object lens in the focusing direction and a mechanism for driving the optical pickup in the tracking direction are dispensed with. Therefore, the time for focusing the laser beam and the time for tracking are reduced, and the weight of the device is reduced and, furthermore, the energy consumption is reduced as compared with the case where a mechanical driver is employed, resulting in an optical pickup device with a simplified driving mechanism, that realizes speedup and energy saving in focusing and tracking.
According to a second aspect of the present invention, there is provided an optical pickup device for irradiating a data recording layer of a disk type data recording medium with a laser beam emitted from a light source, comprising: an object lens that is deformable by a force applied from the outside, and converges the laser beam emitted from the light source to apply it onto the data recording layer; a piezoelectric element that deforms when a voltage is applied, and then applies a force to the object lens; and a control means for controlling the position of focus of the laser beam by applying a voltage to the piezoelectric element to deform the piezoelectric element so that the object lens is deformed by a force applied from the deformed piezoelectric element. In the optical pickup device so constructed, focusing of the laser beam and tracking can be electrically carried out, and a mechanism for driving the object lens in the focusing direction and a mechanism for driving the optical pickup in the tracking direction are dispensed with. Therefore, the time for focusing the laser beam and the time for tracking are reduced, and the weight of the device is reduced and, furthermore, the energy consumption is reduced as compared with the case where a mechanical driver is employed, resulting in an optical pickup device with a simplified driving mechanism, that realizes speedup and energy saving in focusing and tracking.
According to a third aspect of the present invention, in the above-mentioned optical pickup device, when a plurality of disk type data recording mediums having data recording layers of different depth positions are employed, said control means controls the position of focus of the laser beam by deforming the object lens so that the laser beam is focused on each of the data recording layers. In the optical pickup device so constructed, an object lens driving mechanism and a double-focus lens, which have conventionally been required for hocusing the laser beam on the data recording layers of the respective data recording mediums, are dispensed with. Therefore, the time for focusing the laser beam and the time for tracking are reduced, and the weight of the device is reduced and, furthermore, the energy consumption is reduced as compared with the case where a mechanical driver is employed, resulting in an optical pickup device with a simplified driving mechanism, that realizes speedup and energy saving in focusing and tracking.
According to a fourth aspect of the present invention, there is provided an optical pickup device for reproducing signals from a data recording layer of a disk type data recording medium, or reproducing and recording signals from/into the data recording layer, using a laser beam emitted from a light source, and this optical pickup device comprises: a concave reflection mirror as a deformable concave mirror, for reflecting the laser beam; at least one piezoelectric element for deforming the concave reflection mirror; and a piezoelectric element control circuit for controlling the position of focus of the laser beam by applying a voltage to the piezoelectric element to deform the concave reflection mirror. In the optical pickup device so constructed, the laser beam can be focused on the recording medium, and the position of the focus can be finely adjusted in the focusing direction and the tracking direction, without using an object lens, an object lens holder, an object lens adjustment means, and a tracking direction fine-adjustment means. Accordingly, it is not necessary to provide the data recording/reproduction means with an object lens, an object lens holder, an object lens adjustment means, and a tracking direction fine-adjustment means and, further, the piezoelectric element control circuit can be disposed outside the data recording/reproduction means, whereby the weight of the data recording/reproduction means is reduced. This weight reduction leads to weight reduction of the part to be driven by the driving means, resulting in reduced power consumption and high-speed operation. Further, since fine adjustment of the focus position in the focusing direction and the tracking direction can be performed by applying a voltage from the piezoelectric element control circuit to the piezoelectric element, the driving mechanism such as the focus position fine-adjustment means is reduced, resulting in high-speed adjustment of focus position and reduced power consumption.
According to a fifth aspect of the present invention, there is provided an optical pickup device for reproducing signals from a data recording layer of a disk type data recording medium, or reproducing and recording signals from/into the data recording layer, using a laser beam emitted from a light source, and this optical pickup device comprises: a concave reflection mirror as a deformable concave mirror, comprising a concave piezoelectric element, a conductive coating applied to the inner surface of the piezoelectric element, reflecting the laser beam, and having electrical conductivity, and plural electrodes disposed on the outer surface of the piezoelectric element; and a piezoelectric element control circuit for controlling the position of focus of the laser beam by applying voltages between the conductive coating and the plural electrodes to deform the concave piezoelectric element so that the concave reflection mirror is deformed. In the optical pickup device so constructed, the laser beam can be focused on the recording medium, and the position of the focus can be finely adjusted in the focusing direction and the tracking direction, without using an object lens, an object lens holder, an object lens adjustment means, and a tracking direction fine-adjustment means. Accordingly, it is not necessary to provide the data recording/reproduction means with an object lens, an object lens holder, an object lens adjustment means, and a tracking direction fine-adjustment means and, further, the piezoelectric element control circuit can be disposed outside the data recording/reproduction means, whereby the weight of the data recording/reproduction means is reduced. This weight reduction leads to weight reduction of the part to be driven by the driving means, resulting in reduced power consumption and high-speed operation. Further, since fine adjustment of the focus position in the focusing direction and the tracking direction can be performed by applying a voltage from the piezoelectric element control circuit to the piezoelectric element, the driving mechanism such as the focus position fine-adjustment moans is reduced, resulting in high-speed adjustment of focus position and reduced power consumption. Moreover, since the concave reflection mirror itself deforms, the focus position can be controlled in a wide range.
According to a sixth aspect of the present invention, in the above-mentioned optical pickup device, when a plurality of disk type data recording mediums having data recording layers of different depth positions are employed, said piezoelectric element control circuit controls the position of focus of the laser beam by deforming the concave reflection mirror so that the laser beam is focused on each of the data recording layers of the respective disk type data recording mediums. Therefore, a mechanical system, which has conventionally been required for focusing the laser beam on the data recording surface of each data recording medium is dispensed with, and the weight of the data recording/reproduction means is reduced, whereby the weight of the part to be driven by the driving means is reduced, resulting in reduced power consumption and high-speed operation.
According to a seventh aspect of the present invention, in the above-mentioned optical pickup device, the concave reflection mirror generates plural focuses of the laser beam. Therefore, the optical pickup device can read data simultaneously from plural recording tracks on the recording medium without using an image sensor or the like. Further, since the optical pickup device can generate a single laser focus, it can be applied to, for example, writing of data into a recordable medium such as a CD-R. Furthermore, when a single wide laser beam is used, influences of the boundaries between the respective focuses of the concave reelection mirror are reduced.
According to an eighth aspect of the present invention, in the above-mentioned optical pickup device, the plural focuses of the laser beam generated by the concave reflection mirror are independently applied to plural tracks of the disk type data recording medium. Therefore, the optical pickup device can read data simultaneously from plural recording tracks on the recording medium without using an image sensor or the like.